---
title: "Get image dimensions in C#"
url: https://recursiveai.org/oneimage/cookbook/get-image-size/
description: "Get an image’s width, height and format in C# without loading it: read only the headers of a JPEG, PNG, GIF, WebP or TIFF, and get the displayed size of phone photos. Runnable code with OneImage."
version: "1.10.4"
---

# Get image dimensions in C#

Call `Image.Identify` on the file: it reads only the headers and returns the width, height, format, frame count and metadata, without decoding any pixels. For the size a phone photo is shown at, take `Width` and `Height` from `Image.Load`, which applies the EXIF orientation. The program below checks NASA’s “Blue Marble” photograph and a public test photo stored sideways.

```shell
dotnet new console -o ImageSize && cd ImageSize
dotnet add package RecursiveAI.OneImage --version 1.10.4
curl -L -o photo.jpg \
  https://images-assets.nasa.gov/image/as17-148-22727/as17-148-22727~orig.jpg
repo=https://raw.githubusercontent.com/recurser/exif-orientation-examples
curl -L -o phone.jpg $repo/master/Portrait_6.jpg
```

OneImage needs the .NET 10 SDK. Put this in `Program.cs` and run `dotnet run`:

```csharp
using OneImage;

foreach (string file in new[] { "photo.jpg", "phone.jpg" })
{
    // Headers only: fast even for very large files.
    ImageInfo info = Image.Identify(file);
    Console.WriteLine($"{file}: {info.Format.Name}, "
                    + $"stored {info.Width}x{info.Height}, "
                    + $"{info.Frames.Count} frame(s), "
                    + $"orientation {info.Metadata.Orientation}");

    // Load is lazy too, and reports the upright size.
    Image image = Image.Load(file);
    Console.WriteLine($"{file}: displayed {image.Width}x{image.Height}");
}
```

```text
photo.jpg: jpeg, stored 4579x4579, 1 frame(s), orientation 1
photo.jpg: displayed 4579x4579
phone.jpg: jpeg, stored 1800x1200, 1 frame(s), orientation 6
phone.jpg: displayed 1200x1800
```

Orientations 5 to 8 swap width and height, so a phone photo stored landscape is shown portrait. Use the displayed size for layout, `<img>` attributes and crop coordinates; use the stored size to check a file against limits.

## Check uploads without exceptions

`TryIdentify` returns `false` for data that isn’t an image, is damaged, or is over the size limits, so it is a cheap gate for uploads. It takes a path, a `Stream` or bytes:

```csharp
using OneImage;

byte[][] uploads = [File.ReadAllBytes("photo.jpg"), "not an image"u8.ToArray()];

foreach (byte[] bytes in uploads)
{
    if (Image.TryIdentify(bytes, out ImageInfo? info))
    {
        Console.WriteLine($"{info.Format.Name} {info.Width}x{info.Height}");
    }
    else
    {
        Console.WriteLine("rejected: not a supported image");
    }
}
```

```text
jpeg 4579x4579
rejected: not a supported image
```

## Limits

- **The format is detected from the content**, not the file name. Formats the core doesn’t read, such as HEIC and AVIF, are rejected.
- **SVG, PSD and PDF** report their size only when their add-on format is registered in `LoadOptions`. An SVG’s size comes from its `width`, `height` or `viewBox`; a PDF page’s from its size in points and the render DPI.
- **I/O errors still throw.** `TryIdentify` returns `false` for bad image data, not for a missing file.

For the camera, date and GPS position, see [Read EXIF data](https://recursiveai.org/oneimage/cookbook/read-exif-data/). Errors and limits are in the [guide](https://recursiveai.org/oneimage/docs/guide/#errors).